Most passenger cars presently produced are provided with a so-called driver seat air bag and an assistant driver seat air bag, each of which is caused to rapidly inflate between a passenger and a cab structure in an automobile when the front face of the automobile collides (head-on collision) against another automobile or an obstacle.
In recent years, in order to protect a passenger's head not only in head-on collision but also when a side of an automobile collides (lateral collision) against another automobile or an obstacle, a curtain bag system begins to be really mounted, in which system a curtain bag folded and stored in a ceiling part above a side window of an automobile or a pillar part develops and inflates in a manner to cover a side window portion in a collision.
Conventionally, a curtain bag shown in Patent Document 1 is known as an example of a curtain bag. As shown in FIG. 19, the curtain bag shown in the Patent Document 1 comprises two pieces of cloth provided with a coating and joined at an outer peripheral joint part 101 provided at outer peripheral edges thereof to define an outer peripheral shape of a bag, and at an inner peripheral joint part 102 provided inwardly of the outer peripheral joint part 101. The inner peripheral joint part 102 defines an inflated shape of an inflating portion (a portion inflated by introduction of gases) and is provided to assume a linear, curvilinear, or U-shaped configuration, which consists of a combination of the former two configurations, continuous to the outer peripheral joint part 101. Also, the curtain bag shown in the Patent Document 1 includes a gas inflow port 103, to which a gas generator (inflator) is connected, on a rear and upper portion of the bag.
Also, conventional curtain bags include ones having an inner joint part, which is independent of an outer peripheral joint part and shown in FIG. 20 in Patent Document 2, or FIG. 21 in Patent Document 3.
In forming the outer peripheral joint part and the inner joint part, a system by means of machine-sewing and a system (referred below to as OPW system), in which a weaving machine on which a Jacquard machine is mounted is made use of to cross threads in predetermined positions and in a predetermined configuration at a weaving stage to form a joint part, are put to practical use. Also, there exists a type, in which a gas inflow port is provided on an upper portion of a bag. Further, curtain bag systems include ones of two kinds, that is, one (first impact accommodating type), in which a passenger is simply protected immediately only after lateral collision, and one (roll over accommodating type), which takes account of protection of a passenger also in the case where an automobile turns sideways after lateral collision.    Patent Document 1: U.S. Patent Specification No. 60/10,149    Patent Document 2: German Utility Model Specification No. 29903409    Patent Document 3: U.S. Pat. No. 5,566,977